1. Field of the Invention
The present invention relates to a centrifugal master clutch and a vehicular transmission system utilizing same. In particular, the present invention relates to an automated vehicular transmission system comprising an engine, a multiple ratio transmission, a centrifugally operated master friction clutch for drivingly coupling the engine to the transmission and a controller for controlling fueling of the engine during vehicle launch conditions, as a function of throttle position and other sensed system operating conditions such as at least one of engine speed, transmission input shaft speed, transmission output shaft speed, engine torque and engaged gear ratio.
More particularly, a preferred embodiment of the present invention relates to a start control method/system for a vehicular automated mechanical transmission system utilizing a centrifugal master friction clutch controlled solely by engine speed and a controller for controlling engine fueling during vehicle launch conditions.
2. Description of the Prior Art
Automated mechanical transmission systems not requiring the vehicle driver or operator to operate the vehicle master clutch (so called xe2x80x9ctwo-pedal systemsxe2x80x9d), and clutch controls and actuators therefore, are known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,081,065; 4,361,060; 4,936,428; 5,439,428; 5,634,867; 5,630,773; 5,960,916 and; 5,947,847, the disclosures of which are incorporated herein by reference. These systems are not totally satisfactory as separate clutch actuators, sensors and/or, electrical and/or fluid power (i.e., compressed and/or hydraulic) connections thereto are required which adds to the expense of providing, assembling and maintaining such systems.
Centrifugally operated friction clutches are well known in the prior art and typically include a driving input member driven by a prime mover, usually an electric motor or internal combustion engine, and weights rotatable with the driving member which, upon rotation of the driving member, will move radially outwardly under the effect of centrifugal force to cause the driving input member to frictionally engage a driven output member. Examples of centrifugally operated clutches may be seen by reference to U.S. Pat. Nos. 3,580,372; 3,580,372; 3,696,901; 5,437,356; 3,810,533; 4,819,779; 5,441,137; 5,730,269; and; 4,610,343, the disclosures of which are incorporated herein by reference.
Fully or partially automated mechanical transmission systems that, upon determining that a dynamic shift from a currently engaged ratio into neutral and then into a target ratio is desirable, will, while maintaining the vehicle master friction clutch engaged, initiate automatic fuel control to cause reduced torque across the jaw clutches to be disengaged, are known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,850,236; 5,820,104; 5,582,558; 5,735,771; 5,775,639; 6,015,366; and 6,126,570, the disclosures of which are incorporated herein by reference. These systems include systems that attempt to fuel the engine to achieve a sustained zero driveline torque, and systems which force torque reversals, see U.S. Pat. No. 4,850,236. These systems, upon sensing a neutral condition, will, while maintaining the master clutch engaged, cause the engine to rotate at a speed determined to cause synchronous conditions for engaging the target ratio.
Vehicular driveline systems, especially for heavy-duty vehicles, utilizing centrifugal clutches have not been satisfactory as the engines were typically controlled by throttle device position, not on a closed loop basis based upon a target engine speed and/or engine torque, and thus did not provide acceptable control for smooth vehicle launch and low speed operation. Prior art vehicular driveline systems utilizing centrifugal master clutches where not provided with clutches having damage and/or overheating protection and/or were not configured to lock up and release at engine speeds selected to permit dynamic shifting with the master clutch engaged.
In accordance with the present invention, the drawbacks of the prior art are reduced or minimized by the provision of a centrifugal master friction clutch, and a vehicular automated transmission system utilizing same, which utilizes closed loop control to provide acceptable performance for heavy duty vehicle launch operations and low speed operation and is configured to allow dynamic shifting with the master clutch engaged. Preferably, the closed loop control will provide protection from damage and/or overheating.
The above is accomplished by providing a centrifugal clutch structure which will initially lockup at an engine speed below the speed at which upshifts are required and will not release from a lockup condition at engine speeds above (i) the highest speeds at which down shifts are required and (ii) the lowest allowable expected engine speed after completion of an upshift and by controlling fueling of the engine during launch to cause engine speed and/or engine torque to equal or not exceed a target value determined as a function of sensed input signal values indicative of two or more of throttle device position, engine speed, engine torque, transmission input shaft speed, transmission output shaft speed, transmission engaged ratio and clutch slip.
The centrifugal master clutch requires no external clutch actuator or sensor, and no connections to mechanical linkages, electrical power and/or fluid power.
Accordingly, it is an object of the present invention to provide a new and improved centrifugally operated vehicular master friction clutch and automated mechanical transmission system utilizing same.
This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.